Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, and the like. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources.
A wireless communication network may include a number of base stations or Node-Bs that can support communication for a number of user equipments (UEs). A UE may communicate with a base station via downlink and uplink. The downlink (or forward link) refers to the communication link from the base station to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the base station.
In some wireless communication systems, a user equipment (UE) may be capable of supporting concurrent connections with multiple access points using techniques which may be referred to as multiflow operation. The multiple access points may be associated with the same or different radio access technologies (RATs). For example, a UE may be simultaneously connected to a wireless local area network (WLAN) and a Long Term Evolution (LTE) or LTE-Advanced (LTE-A) network.
The networks may support techniques for utilizing feedback from the UE in adapting communication links to channel conditions seen by the UE. For example, the UE may report channel state information (CSI) to each network and the networks may adapt various communication parameters used for communication over the links. The adapted communication parameters may include, for example, modulation and coding scheme (MCS), rank, and precoding for downlink transmissions.
The base station and the UE may each use multiple antennas when communicating with each other. Multiple antennas at the base station and UE may be used to take advantage of antenna diversity schemes that may improve communication quality and reliability. There are different types of techniques that may be used to implement an antenna diversity scheme. For example, transmit diversity may be applied to increase the signal to noise ratio (SNR) at the receiver for a single data stream. Spatial diversity may be applied to increase the data rate by transmitting multiple independent streams using multiple antennas. Receive diversity may be used to combine signals received at multiple receive antennas to improve received signal quality and increase resistance to fading. Multiple antenna technologies for communicating multiple data streams may be known as multiple-input multiple-output (MIMO) communications.